Controlling the intracellular dynamics of neuronal model systems*

Excitable tissues in the body have unique properties that allow for the transfer of information between individual cells and across larger scales. For example, recent work has investigated the spatiotemporal dynamics of electrical activity propagation in neural and cardiac tissues in both in vivo and in vitro settings. In the present work, we study how the intracellular behavior of in vitro cultures of primary rat cortical neurons can be tuned and controlled with electric fields. However, in addition to the effects on electrical signal propagation that are traditionally studied, we are also interested in the morphological responses of neurons to these electric fields with the goal of understanding the interaction between electrical activity propagation and cytoskeletal dynamics, particularly of actin. To accomplish this goal, we do the following: 1) apply electric field stimulation to the in vitro neuronal culture, 2) image changes in transmembrane potential or intracellular actin, and 3) quantify the intracellular response. We show that the dynamics of actin change significantly over time as the structural components of neurons (axons and dendrites) mature and become more stable. Moreover, we show that neurons can be electrically activated by direct current (DC) electric fields, but the degree and complexity of the response to the field strongly depends on the age of the cells with a more prevalent response observed as the neurons (and therefore, synapses) have matured. In sum, we have found that we can tune neuronal cell behavior with electric fields, and in future work, we hope to apply these same perturbations to other cells and make inferences about the intracellular behavior of other electrically excitable cell types.